Type of pot to use in greenhouse/conservatory

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poppy123
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Type of pot to use in greenhouse/conservatory

Postby poppy123 » Fri Mar 26, 2021 12:07 pm

Hello. Does anyone have any advice on what is the best pot to use in a double glazed greenhouse/conservatory please? I am thinking of moving my tomato growing from my polytunnel to the greenhouse. I usually grow them straight in the ground. Also hope to grow peppers, chilli and aubergine. I am wondering if black plastic might get too hot. What are the pros and cons of terracotta? I wanted a lean to greenhouse alongside the house, but I was worried about single pane glass in the storms (we are on Wild West Wales coast). So we have decided to go double glazing - more of a conservatory but to be used as a greenhouse. Thank you.
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Monika
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Re: Type of pot to use in greenhouse/conservatory

Postby Monika » Fri Mar 26, 2021 4:13 pm

Black plastic pots have never got too hot for me and I think terracotta might dry out too quickly and would certainly be very heavy to move when full.
My preferred method for growing tomatoes and peppers is in growbags with growpots 'screwed' into them. These are also filled with growbag compost. It gives the plants more root space and also lets you water them easily into the growpot surround. I used to use just bottomless plastic pots 'screwed' into the growbags, but the growpots are so much easier to use and have now lasted me for years and years.
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Re: Type of pot to use in greenhouse/conservatory

Postby Westi » Fri Mar 26, 2021 7:59 pm

Black plastic pots will be OK but need to be deep as the deeper you plant the toms the more roots form so they are getting more nutrients & will be more prolific. Grow bags standing upright are good but ugly so perhaps you could make a frame to support them & also hide them & this would last years or maybe just paint them? These bags are also deep enough for a cane to support their weight when heavy with fruit as well when pushed right to the bottom.
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Re: Type of pot to use in greenhouse/conservatory

Postby poppy123 » Sat Mar 27, 2021 11:16 am

Thank you both for your replies. Also raising the point about how I am going to support them. Builders haven't started work yet so I have some time to think about it!
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sally wright
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Re: Type of pot to use in greenhouse/conservatory

Postby sally wright » Sat Mar 27, 2021 12:53 pm

I normally grow my tomatoes in pots and I use a minimum size of 20L for a standard cordon (indeterminate) variety grown to 5 trusses; but I will use bigger pots if I have them available for plum and beefsteak types. This is because they are more prone to blossom end rot (mainly caused by irregular watering) so they benefit from the extra water storage/buffering capacity of the larger volume of compost. They also have bigger fruit which can cause them to be very prone to falling over without the weight of the bigger pot volume.

If you turn a pot upside down then you will see the volume (most pots are measured this way these days) stated on the bottom. I normally grow mine in a polytunnel with a black fabric floor so I don't usually bother with saucers as they root into the floor through the fabric. You can fit three pots (20L) onto a growbag tray so I would recommend getting some of those to help with the watering in the heat (?) of summer.

I would also recommend using a soil based blend of compost or make your own (much cheaper). If you cannot find such a blend in your area then I would suggest adding one part sand to 4 parts of whatever compost you can find. I would also recommend adding pelleted slow release fertilizer to the mix at 3g/Litre of compost. Tomatoes are greedy feeders - especially so when grown in pots.

To make your own tomato compost you will need garden soil, compost from your garden compost bin and slow release fertilizer. A 1kg tub of slow release fertilizer will cost about £6 and will make 250L of home made compost. I usually do about 40% garden soil (5 x 20L pots full)and 60% home made compost (7 x 20l pots full) (if your soil is heavy clay use 30% soil and 10% sand or grit) Use a bucket or pot that you know the literage of to measure out the ingredients. Try to put a little bit of the fertilizer between each layer and then mix the compost by shovelling it into another heap. Repeat this step three times to ensure an even blend of the ingredients. You need to add the fertiliser at 4g per litre because there is no other fertiliser added. Fill the pots as full as you can because this home made compost does settle quite a bit after a few weeks. This mix will make 12 pots (20L).

This mix works very well for Aubergines and peppers too. For cucumbers I up the fertilizer level to 5g/L of compost

You will still need to liquid feed once the first truss has set (the baby fruit has started to form).

I would recommend that ventilation and shading issues are considered at the time of construction as these will directly affect the quality of the tomatoes. Greenback, splitting and as I mentioned earlier blossom end rot can all be caused by water stress and overheating.

Keeping the tomatoes upright can either be done with string fastened to the roof in some way or by canes. This is when using the largest pots you can is very useful as they will help to keep the plant and cane upright.

In the polytunnel I cannot fasten them to anything solid so this is how I keep the tomato plants stable. I make 2 rows of pots about 18 inches (45cms) between the pots and the rows. I am using 6 foot (180cm) canes for this. I then lean a pair of canes together and tie them at the top. I do this all the way along the row and then put 1 or 2 canes into the 'V' shapes at the top and tie the whole row together. The whole thing looks rather like a bean row once done. At the end of the season when the plants are really top heavy with fruit I will sit a couple of old bricks into the tops of each pot. If you have no bricks then anything heavy will do - even kitchen bottles filled with water will help.

Regards Sally Wright.
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Re: Type of pot to use in greenhouse/conservatory

Postby Primrose » Sat Mar 27, 2021 4:59 pm

I,ve always grown my peppers in large brown plastic pots and even in heatwaves have found the roots have survived. They don the seem to mind the heat. However in the heat of the day I,ve covered them with fleece to prevent the growing fruit from becoming sun scorched.

Have never used grow bags for tomatoes. I would onky use them for the tumbling varieties whixh don't need support. When i had very little growing space i used large black plastic pots and a bamboo cane to hold the stem upright. I do think if you hope for a reasonable crop you need to add some soil to your compost otherwise there won't be enough nutrients to sustain the olant throughout its life, and feed at least weekly as soon as fruit start appearing.
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sally wright
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Re: Type of pot to use in greenhouse/conservatory

Postby sally wright » Sat Mar 27, 2021 8:47 pm

On re-reading my first post I realise that I have not addressed the initial question of what type of pots to use in your conservatory.

Well my answer is plastic for the following reasons - not in any particular order of merit.

Plastic pots will cause less damage to the floor tiles - either by scratching or, if the tomatoes fall, over the rim of the pot bouncing (or not!) off the floor. Floor tiles are rather expensive and an absolute PAIN to replace if they get damaged.

Cost - plastic pots are much cheaper than ceramic ones - even if you get the posh ones. They won't give the car, your wallet or you a hernia getting them home from the garden centre either. I don't know how many tomatoes you plan on growing in your new conservatory but you are much more likely to find a matching set of plastic pots than you are of ceramic ones AND more likely to find matching replacements as most garden centres change their ceramic ranges every couple of years as fashions change.

Plastic pots will store away easier as they stack neatly and can be stored outside when they are not in use. Lugging terracotta pots up and down the garden to dry storage gets OLD fast.... Though to get the best use out of the plastic pots they should be stored in darkness when not occupied by the tomatoes. Fancy coloured pots especially as they will fade in the light.

Water retention - no not your ankles! Terracotta and even to some extent glazed pots will use a lot more water to keep the plants well watered. They will also get white deposits of limescale and other minerals from the compost forming on the outside of the pots as water evaporates. This looks icky and can start to ping off the outer surface of terracotta pots if it gets too bad.

Plastic pots can be cleaned a lot easier than ceramic ones - which might prove useful at keeping pests and diseases to a minimum.

You will be changing the soil every year, plastic pots will make this less of a weightlifting excercise.

Regards Sally Wright.
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Re: Type of pot to use in greenhouse/conservatory

Postby snooky » Wed Mar 31, 2021 7:25 pm

Following on from what Sally has written about growing pots for tomatoes etc is there an optimum size pot for starting offthe various sized seeds?
Whilst washing 3" pots to start off Sweetcorn seeds I had a sudden thought that it may be that I should be using a bigger size pot or even a smaller one.I just use what I deem appropriate and go from there.Never given it much thought before and just wondered if I was giving that seed the best chance to develope before planting out.
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Re: Type of pot to use in greenhouse/conservatory

Postby Primrose » Wed Mar 31, 2021 7:49 pm

Most of the seedlings you buy from garden centres for example are in very shallow strips and probably need to be potted on or planted out fairly quickly to avoid nutrition starvation but they certainly start off small.
It's often weather dependent of when seedlings get planted out so I'd go for whatever has worked OK for you in the past. It seems to be a very personal thing on what works best for your own growing conditions.
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sally wright
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Re: Type of pot to use in greenhouse/conservatory

Postby sally wright » Wed Mar 31, 2021 9:33 pm

I generally try to have no more than 250 seeds sown to a standard sized seed tray (the A4 size). This is for medium seeds such as tomatoes, peppers and brassica seeds. For smaller seeds you could go up in seed count but I don't usually do that as they still need the space to grow to a size at which they can be handled to be pricked out. I am a bit of a klutz and because of this I will put several varieties of say tomatoes into a standard seed tray rather than doing individual pots; my reason being that I can knock over little pots rather easily and the labels sticking up don't make it any easier. I divide the tray using plant labels into squares and sow into those. It may not work for you but it does for me.

For large seeds (cucumbers, squash and beans then individual cells are much the best way as they can be transplanted without damage to the brittle roots. Doing the squash family I will go with a fairly small (maybe 1" - 2cms) cell size as I will pot them on into 3-4" pots (depending on type and vigour); I take the opportunity of putting the seedling as far down into this pot as possible as they can get rather leggy. This helps to reduce breakages at transplant to final pot/garden time.

For peas and beans I will sow them into 2" - 5cm cells. (24 cells to a standard sized seed tray) Broad beans 2 seeds per cell, runners 2/cell and French climbing and dwarf 4/cell. With the aim of getting them out into the garden before the true leaves appear. Peas go in at 5/cell. As far as I am concerned this growing in cells for these seeds is just a way of getting them germinated quickly and free from mice and other pests.

I have not grown sweetcorn before but I am going to try this year as where I work will, I hope, be having a thanksgiving dinner and I want to grow some of the ornamental kinds for table decorations. I have some slightly larger cell trays with 18 cells/ standard sized seed tray. I plan on putting perhaps 3 seeds per cell and I will try and remember to keep everyone informed on progress.

Regards Sally Wright.
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Re: Type of pot to use in greenhouse/conservatory

Postby Geoff » Wed Mar 31, 2021 10:26 pm

Sweetcorn do really well in rootrainers. You can leave them in for quite a while until they have a solid root system that is easy to transplant and they then grow away strongly. Germination rate is usually high (good job as the sweet F1s aren't cheap) so sow at one per cell and don't waste seed or space.
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sally wright
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Re: Type of pot to use in greenhouse/conservatory

Postby sally wright » Wed Mar 31, 2021 11:07 pm

None of my corn varieties are F1; they are the fancy coloured varieties, red, black and glass corn (it looks so cool in the pictures!).
https://www.premierseedsdirect.com/prod ... n-organic/

Haven't got any rootrainers so cells it will have to be.

Regards Sally Wright.
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